The long-term goal of this 25-year-old research is to discover the principles involved in signal processing in the neuron network in the: vertebrate retina and to produce a mathematical model of the neuron: network based on these principles. There is a set of principles that is particular to the operation of the neuron network and is different from the set of principles that governs ionic or channel mechanisms. At the turn of this century, S. Ramon y Cajal established the neuron doctrine which states that each single neuron functions more or less independently. Golgi, on the other hand, maintained that neurons form a syncytium, the neuroreticulum. Lately, structural as well as morphological evidence is accumulating to suggest that many neurons in the retina form a syncytium which is referred to as a neuron space (in which neurons are tightly coupled) or a neuron cluster (in which neurons are loosely coupled). For example, the horizontal and transient amacrine cells form two independent spaces and sustained amacrine cells form two independent clusters. Our two main goals are: l) Identification of signal transmission between neurons in the inner retina. We will study the way in which signals are transmitted between neurons in a space or in a cluster and the way in which spaces and. clusters interact with each other. In this series of experiments, the space and cluster will also be identified morphologically by intracellular injection of neuro-tracers. 2) The receptive field will be explored by the use of many types of light stimulus in an effort to define a field in time and space (spatiotemporal receptive field) and to try to decompose a response into two components, one that is intrinsic to the cell and the other that reflects the activity of the network.